The present invention relates to a recording apparatus, a recording head usable therewith, and a substrate for a recording head. The recording apparatus is used as an output machine for a copying machine, a facsimile machine, a word processor, a host computer or the like. More particularly, it relates to the same in which a plurality of recording elements are used, which are selectively driven by integrated circuit for the driving.
Various types of recording machines are known. Among them, a liquid ejection recording apparatus in which ink is ejected through ejection outlets provided for the respective recording elements, are desired because of the advantages of the low noise non-impact recording operation, capability of high density recording, capability of high speed recording. The recent demands for such apparatus includes the compactness and low cost.
Among the liquid jet recording apparatus, a type using electromechanical converters (piezoelectric elements, for example), a type using electrothermal transducers and a type using pairs of electrodes supplied with a voltage to eject liquid droplets, are known. Further among them, an ink jet recording apparatus of a type in which the recording liquid is ejected using thermal energy, has been commercialized because of its advantages that the liquid ejection outlets (orifices) can be arranged at high density with the result of capability of high resolution recording and that the multi-nozzle (orifice) arrangement is relatively easy with the result of capability of the high speed printing.
In a known recording head used with the recording apparatus of this type, a plurality of recording elements are arranged in a line, and the recording elements are divided into plural blocks each having several tens recording elements, and several or several tens driving circuits for the respective blocks, are formed on one substrate as integrated circuits. The recording elements are selectively driven in accordance with image data by the driving circuits, so that the recording is effected on the recording material such as paper.
These recording heads are particularly noted because of its high resolution and high speed recording. However, further reduction of the cost and the size and the improvement of the performance, color printing function, or the like are desired. Referring to FIG. 29, there is shown a conventional substrate (heater board) having recording elements thereon and a schematic sectional view of the ink jet recording head using the substrate.
In FIG. 29, (d), reference numeral 1 designates a heater board having thermal energy generating means in the form of an electrothermal transducers 2 a top plate 17 is provided with grooves constituting a part of passages for ink 3. The ink 3 is supplied through the passages formed by the heater board 1 and the top plate 17, as indicated by an arrow A. The ink is then heated by the electrothermal transducers 2 on the heater board 1 so that the ink is ejected through the ejection outlets 5 in the direction indicated by an arrow B. In FIGS. 29, (a)-(c), show arrangements of various elements in the heater board 1. It includes electrical leads for electrically connecting various elements, diode arrays 7, and pads 8 for external electrical connection. In the arrangement of FIG. 29, (a), the electrothermal transducers 2, the electrical leads 6, the diode arrays 7 and the pads 8, are disposed in the order named from the ejection outlet 5 side.
In FIG. 29, (b), the electrical connection between various elements are the same as in FIG. 29, (a), but the electrical leads 6 portion and the diode array 7 portions are mixed. In FIG. 29, (c), the electrothermal transducers and the pads 8 are arranged with one-to-one relation therebetween.
In an arrangement of FIGS. 30, (a), (b) and (c), an ink supply port 9 is formed in the heater board 1 having the electrothermal transducer, as contrasted to the case of FIG. 29. In this case, the ink is supplied from the backside of the substrate cover as indicated by an arrow A, and the ink is ejected in a direction substantially perpendicular to the surface of the substrate 1, as indicated by an arrow B.
As for the wiring in the heater board shown in FIG. 29 or 30, two types are known. In one of them, as shown in FIG. 29, (c), and FIGS. 30, (a)-(c), and FIG. 31 designating the equivalent circuit, the electric signals are supplied from the pads 8 to the electrothermal transducers in one-to-one relation (direct drive type). In the other type, as shown in FIGS. 29, (a) and (b) and FIG. 32 showing an equivalent circuit, a matrix arrangement using diodes are used, in which the electrothermal transducers are selectively driven by selective drive voltage application between segment pads SEG and common pads (matrix drive type).
In the direct type shown in FIG. 31, n pads 8 are required for n ejection heaters (electrothermal transducers) 2. In addition, VH pad is required, and therefore, (n+1) pads are required in total. Since the pads 8 are directly connected to the ejection heaters 2, a large current such as approx. 150 mA. With a pulse width of 7 xcexcS in a 360 dpi recording head for plain paper according to an example of experiments by the inventors, flows therethrough. In addition, the same current multiplied by n, flows through the VH pad. Thus, all the electrical leads have to be designed for large current. Because of the number and large size of the pads, a large area is required for the wiring with the result of bulky substrate and recording head and high manufacturing cost. From the standpoint of the main assembly of the recording apparatus, the connecting portion and the wiring therein are complicated due to the large number of the pads.
FIG. 32 shows another type of matrix drive system. The number of electrical leads and the pads is decreased as compared with the above-described direct type. However, when n ejection heaters 2 are used, the minimum number of pads is 2{square root over (n)} (when 2{square root over (n)} is not an integer, the value is rounded, and added by 1) are required at minimum. The electric current flowing through the common electrode (COM) pad is the electric current per one ejection heater multiplied by the number of ejection heaters connected with the matrix, as the case may be, and therefore, the electrical leads 12 have to be designed for the large current.
Generally, in an ink jet recording head, there is a liability that the pressure wave at the time of bubble formation is transmitted toward upstream (toward a common liquid chamber) in the form of a back wave, with the result of fluid cross-talk among nozzles. Therefore, simultaneous drives of adjacent nozzles may result in instable ejection due to the back wave. In view of this, it is desirable that the simultaneous drives are effected for nozzles which are spaced greatly, from the standpoint of stabilized ejection and high image quality. However, in the case of the above-described matrix drive circuit, if the common electrode simultaneously drives a large number of different driving elements (COM), large current flows through the thin segment (SEG) leads with the result of potential difference within the leads. If this occurs, the electrothermal transducers are not supplied with proper electric energy. For this reason, there is a problem that the large number of elements are not driven.
The problem of the large number of pads and the complicated wiring in the heater board, is more significant in the case of color recording.
In order to accomplish the color recording, the recording apparatus is provided with a plurality of recording head for the respective colors.
FIG. 33 is a block diagram of a circuit structure for a conventional liquid jet recording apparatus for color recording. Designated by references 2C, 2Y and 2M are recording elements (electrothermal transducers) for cyan, yellow and magenta recording. Several tens of such elements are used. Function elements 10 are for controlling power supply to the recording elements. A shift register circuit 11 aligns the image data, corresponding to the recording elements. It is directly connected with a latching circuit 12 storing data for the recording elements. By using an output of an AND gate receiving as inputs an output of the latching circuit and an output of another AND gate connected at the input to the signal lines 14 and 15 for controlling the power supply period to the recording elements, the recording element can be supplied with the power during the output period of the first mentioned AND gate. In the Figure, the zone indicated by the broken line is formed on the substrate, and therefore, the electrothermal transducers 2, function element array (transistor array 10 in this embodiment) for selectively driving the electrothermal transducers 2, are formed on the substrate.
With this structure, however, the number of contacts between the recording head carriage (main assembly) and the electrical leads is still large with the result of complicated driving circuit. Therefore, the design and productions are still difficult.
U.S. Pat. No. 5,030,971 discloses that in order to reduce the size of the color recording apparatus, the substrates for the different color are made integral. In the U.S. Patent, the elements for the four colors are formed on the same substrate. The driving circuit in this patent is in the diode matrix type, and therefore, the number of electrical leads is small as compared with the case of the direct driving system, and therefore, the size of the recording head itself can be reduced. This will be satisfactory if the number of electrothermal transducers is small. However, if the number is increased to meet the demand for the high speed recording, for example, the number of electrical leads and the pads increases accordingly, with the result that the above-described problem arises.
As regards the manufacturing of the substrate, the yield decreases with increase of the number of recording elements (electrothermal transducers), since the number of diodes and transistors also increases. Also, the yield in the formation of the ink ejection outlets or the like by connection with the substrate, and therefor, it has been difficult to manufacture the substrate having a large number of recording elements.
In the case of the substrate having the supply port as shown in FIG. 30, the utilization factor of the silicone wafer constituting the substrate can not be increased with the result of high cost.
Accordingly, it is a principal object of the present invention to provide a substrate, a recording head using the same and a recording apparatus using the same, in which the wiring on the substrate is simplified.
It is another object of the present invention to provide a substrate, a recording head using the same and a recording apparatus using the same in which a number of pads on the substrate is reduced, so that a larger number of recording elements can be formed on the substrate.
It is a further object of the present invention to provide a substrate, a recording head using the same and a recording apparatus using the same, wherein even when a large current is used, the current is not concentrated locally on thin electrical leads.
It is a yet further object of the present invention to provide a substrate, a recording head using the same and the recording apparatus using the same in which a number of electrical connection pads is increased, so that the wiring can be simplified and that the manufacturing is easy, the size is reduced and the cost is reduced.
According to an embodiment of the present invention, there is provided a substrate having plural recording elements and electrical leads for supplying electric signals to the recording elements, comprising: electrical contacts for external electrical connection for reception of image signals used for driving the recording elements; and a processing circuit for converting signals which are serially supplied to the connecting contact to parallel signals to be applied to the recording elements.
According to another embodiment of the present invention, there is provided an ink jet recording head having a substrate with plural recording elements and passages for supplying liquid to a neighborhood of the recording elements, the improvement residing in the substrate, comprising: electrical contacts for external electrical connection for reception of image signals used for driving the recording elements; and a processing circuit for converting signals which are serially supplied to the connecting contact to parallel signals to be applied to the recording elements.
According to a further embodiment of the present invention, there is provided a recording apparatus for effecting recording operation with ink droplets ejected, comprising: a recording head having a structure defined above; and electrical signal contact connected with the recording head to supply the signal thereto.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.